1) Field of the Invention
The present invention relates to a developing device with a developer supplier used in an image formation apparatus such as a copying machine, a laser printer, a facsimile or the like, wherein an electrostatic latent image is electrostatically developed with a developer.
2) Description of the Related Art
Generally, in an image formation apparatus such as an electrophotographic recording apparatus, the following processes are typically carried out:
a) a uniform distribution of electrical charges is produced on a surface of an electrostatic latent image carrying body;
b) an electrostatic latent image is formed on a charged area of the body surface by an optical writing means such as a laser beam scanner, an LED (light emitting diode) array, a liquid crystal shutter array or the like;
c) the latent image is developed as a visible image with a developer or toner, which is electrically charged to be electrostatically adhered to the latent image zone;
d) the developed and charged toner image is electrostatically transferred from the body to a recording medium such as a cut sheet paper; and
e) the transferred toner image is fixed and recorded on the cut sheet paper by a toner image fixing means such as a heat roller.
Note, typically, the electrostatic latent image carrying body may be an electrophotographic photoreceptor, usually formed as a drum, called a photosensitive drum, having a cylindrical conductive substrate and a photoconductive insulating film bonded to a cylindrical surface thereof.
As one type of developer, a two-component developer is well known, which is composed of a toner component (colored fine synthetic resin particles) and a magnetic component (magnetic fine carriers). Usually, a developing device using this type of developer includes a vessel for holding the two-component developer, wherein the developer is agitated by an agitator provided therein. This agitation causes the toner particles and the magnetic carriers to be subjected to triboelectrification, whereby the toner particles are electrostatically adhered to each of the magnetic carriers. The developing device also includes a magnetic roller provided in the vessel as a developing roller in such a manner that a portion of the magnetic roller is exposed therefrom and faces the surface of the photosensitive drum. The magnetic carriers with the toner particles are magnetically adhered to the surface of the magnetic roller to form a magnetic brush therearound, and by rotating the magnetic roller carrying the magnetic brush, the toner particles are brought to the surface of the drum for the development of the electrostatic latent image formed thereon.
In this developing device, a ratio between the toner and magnetic components of the developer body held in the vessel must fall within a predetermined range before a stable development process can be continuously maintained. Accordingly, preferably, the developing device is provided with a developer supplier from which a toner component is supplied to the developer body held in the vessel, to supplement the toner component as it is consumed during the development process, whereby the component ratio of the developer body held by the vessel is kept within the predetermined range.
A one-component developer is also known, which is composed of only a toner component (colored fine synthetic resin particles), and there are two types of the one-component developer; a magnetic type and a non-magnetic type. Namely, each toner particle of the magnetic type one-component developer has a resin part and a magnetic fine powder part, whereas each particle of the non-magnetic type one-component developer has only a resin part. A developing device using the magnetic type one-component developer is also provided with a magnetic roller, which can be constructed in substantially the same manner as that for the two-component developer. Namely, the magnetic type one-component developer also can be brought to the surface of the photosensitive drum by the rotating magnetic roller as in the developing device using the two-component developer. In a developing device using the non-magnetic type one-component developer, a conductive elastic roller, which may be formed of a conductive foam rubber material, is used as a developing roller. When the conductive elastic roller is rotated within a body of the developer held by a vessel, the toner particles are frictionally entrained to be brought to the surface of the photosensitive drum. Also, the developing device using the one-component developer is preferably provided with a developer supplier from which a one-component developer is supplied to the body of developer held in the vessel, to supplement the developer as it is consumed during the development process.
As one type of developer supplier, a cartridge type is well known, which is detachably mounted in the developer vessel. This cartridge type developer supplier includes an outer cylindrical container, and an inner cylindrical container rotatably housed within the outer container and holding a given amount of the developer therein. Each of the outer and inner containers has an outlet port for discharging the developer from the developer supplier, but, before the developer supplier is mounted in the developer vessel, the outlet port of the outer container is not in register with that of the inner container so that the outlet ports are closed to prevent a leakage of the developer from the developer supplier. After the developer supplier is mounted in the developer vessel, the inner container is rotated in the outer container by manually operating a pair of lever elements provided at the end faces of the developer supplier, until the outlet ports are in register with each other, whereby it is possible to take out the developer from the developer supplier through the registered outlet ports, for supplementing the developer to the body of developer held in the vessel. Although a manner of mounting the developer supplier in the developer vessel is shown and explained in a printed matter such as a handbook, a user may frequently forget the manual operation of the lever element for taking out the developer from the developer supplier.
In one type of electrophotographic recording apparatus, in particular, a personal type of electrophotographic printer, a developing device is formed as an exchangeable unit. When the exchangeable developing device cannot be used, i.e., when a developer held therein is consumed, the developing device per se is exchanged for a new one. During shipping of the new developing devices not yet used in a printer, leakage of any developer must be prevented. Accordingly, a vessel of the exchangeable developing device is divided into two chambers by a tape-like seal element: one chamber houses a developing roller; and the other chamber holds a body of developer. Just before the new developing device is incorporated in the printer in exchange for the old developing device, the tape-like seal element is pulled and removed out of the new developing device, and thus a seal for the developer chamber is broken so that the two chambers are in communication with each other. Similar to the detachable developer supplier as mentioned above, a user may frequently forget the removal of the tape-like seal element out of the new developing device. Also, during the exchange of the old developing device for the new developing device, a leakage of developer from the new developing devices may occur because the chamber for the developing roller is in communication with the outside.